1. Field of the Invention
The present invention relates to an image forming apparatus for forming images on sheets, a control method therefor, an image data output control method, and storage media storing programs for executing these methods.
2. Description of the Related Art
Conventional image forming apparatuses such as digital copiers output image data read by a scanner or the like, without changing the direction of the image data so that the output results are rotated through 180° as viewed from a user. This allows fast image processing but necessitates controlling of process positions in performing a punching process, a stapling process, and the like associated with the image processing.
FIGS. 14A to 14D are views showing how an image is processed starting with scanning of the original on an original table and ending with outputting of the image onto a recording sheet.
If an original with a character “” depicted thereon is placed on the original table in such a manner that the lower part of the original as viewed in FIG. 14A is closer to the user, while the upper part is closer to the original table, then the image data are read by scanning the original in the main scanning direction indicated by an arrow m and then in the subscanning direction indicated by an arrow s, as shown in FIG. 14B. Then, as shown in FIG. 14C, the read image data are written in a main direction indicated by an arrow m′ and in a sub direction indicated by an arrow s′, as shown in FIG. 14C and recorded in an image memory. Further, as regards the subscanning direction for the original, the direction in which a recording sheet is conveyed is normally opposite to the direction in which data are written onto the recording sheet. Accordingly, if the image data are read out from the image memory in the direction in which the data were written as shown in FIG. 14C, then the data are output onto the recording sheet with the main scanning direction indicated by an arrow m″ and the subscanning direction indicated by an arrow s″, as shown in FIG. 14D. As a result, the output image obtained is rotated through 180° with respect to the input original image as viewed from the user.
In this manner, the conventional image forming apparatuses can quickly output image data by aligning the direction in which the data are written onto the image memory with the direction in which the data are read out from the image memory.
Further, the image forming apparatuses of this kind have come to be able to handle not only plain paper, OHP sheets, and the like but also various types of recording sheets such as ones having image data previously printed thereon and ones already subjected to a punching process.
With the above described conventional image forming apparatuses, however, if recording sheets are directional or orientation, for example, if they have different image data previously printed thereon or have already been subjected to a punching process, and if an input image is output onto these recording sheets, then the output image obtained may have a direction or orientation different from that of the image data previously formed on the recording sheets or the punch holes obtained by the punching process are formed at a location different from a desired one. Consequently, the user's intended output results may not be obtained.
To avoid such a situation, if, for example, output sheets have any image previously printed thereon, the user himself must perform operations such as setting the recording sheets in the sheet feeding section in a predetermined direction taking the construction of the apparatus into consideration, or must intentionally rotate the output image before outputting it.
The above-mentioned operations, however, are very cumbersome to the user, and when the user himself must perform such cumbersome operations, he is likely to make a mistake in setting the sheets or operating the apparatus, thus failing to obtain desired output images.
For example, with an image forming apparatus having a punching process function, if an image is output onto a recording sheet with punch holes 51 already formed therein as shown in FIG. 15A, further punch holes 52 may be formed in the recording sheet with the punch holes 51 already formed therein, as shown in FIG. 15B, or the direction of the output image may not align with the direction of the punch holes, thus disadvantageously hindering an intended filing operation.